To minimize vibrations from the motor and bearings of a
turntable, it makes sense to eliminate the motor and
bearings. There
is already a magnetically-driven turntable in this
establishment [link] and a maglev one on the market
[link], but I haven't heard of one with an air
film bearing before
this one.
It works by having the platter float on a film of air
generated by small nozzles built into the surface
underneath the platter.
The facing surfaces of the platter and the turntable's
base are slightly conical to keep the platter centered.
The platter's
underside is also shaped with vanes to generate a torque
about its vertical axis from the outward flow of air; the
flow of air
can be regulated to be able to play records of different
rotational frequencies (with differential airflow between
groups of
nozzles at different radii, with the vanes also being
radially limited, to preserve lift but vary torque).
Around the rim of the platter and the corresponding area
on the base, there is a diffuser composed of specially
shaped vanes
and cavities, as well as a ring of foam. This absorbs the
hissing noise of the air that supports the platter.
When the turntable is turned off (with an air valve rather
than an electric switch), the platter slowly spins down
and comes to
rest in the base. No longer supported by air, it rests on
rubber feet, which are shaped to aerodynamically blend
into the vanes.
The compressed air can come from an air compressor in
another room, or even another building, or you can use a
nearly silent
air compressor (widely available, but probably more
expensive than a loud one) inside a soundproof box.
Piston-type air compressors probably typically don't
produce a very clean pressure output—I expect it has a
lot of noise, mostly
from the pulsation of the pistons. Screw compressors are
probably better, but still probably have some pulsation.
Therefore,
the turntable has air pressure low-pass filtering built in.
This consists of a pressure regulator on the input,
followed by a
diaphragm pressure buffer tank, followed by a vane–
flywheel inerter (which is also supported by an air film
bearing). These are
all made of audiophile-grade materials*, of course, as
are the rest of the components.
A pneumatic amplifier/speaker unit [link] is also
available, to use this turntable as a compressed air
gramophone [link] to play
music for a large audience or over loud background
noises. Both apparati are also highly rugged, enabling use
on remote job
sites where compressed air is available from an engine-
powered compressor, but electricity is not. In this case,
you can use the
special high-fidelity audio tube**, available separately, to
connect directly from the turntable's needle to the
speaker's comb
valve, to eliminate all need for electricity.
*any old materials whose properties can be described in
flowery language that makes them seem especially
suited to low-noise,
low-distortion audio playback applications
**a piece of narrow hydraulic hose with a braided
metallic fabric sleeve
N/A [2019-09-28]